Button stem for electron discharge devices



Nov. 23, 1948. 11 HENRYv I 2,454,384

BUTTON STEM FOR ELECTRON DISCHARGE DEVICES Filed May 21, 1946 IN V EN TOR.

Patented Nov. 2 3, 1948 BUTTON STEM FOB. ELECTRON DISCHARGE DEVICES Thomas J. Henry, Newark, N. J assignor to Radio Corporation o'f America, a corporation of Delaware Application May 21, 1946, Serial No. 371,190

10 Claims. 1 The present invention relates to electron 'discharge tubes which more specifically are of "a very small size referred to as sub-miniature type.

As the need has arisen for smaller electronic tubes, the problem of electrostatically shieldin the electrode leads of t e tube from-each other has become greater and more varied. The shielding of the electrode leads within an electron discharge tube has been effected with metal plates of varied forms and arrangements. Furthermore, lead pins extending from the base of the tube have been effectively shielded, for example, by a metallic centering lug grounded through one of the base pins.

Some types of tubes utilize a glass button stem in which the lead pins are sealed. The glass stem is usually provided with an exhaust tubulation through which the electron tube is exhausted after the glass button stem has been sealed to the envelope. To reduce the electrode capacitances in the glass stem itself, grounded metal strips, for example, have been deposited within the exhaust tubulation.

It is evident that such methods of electrostatic shielding have a number of disadvantages. One disadvantage is the necessity of specially designed shielding plates. Furthermore, separate operations are required, in the assembling of the tube, to position and fasten the shield structures in place.

As the size of the tube became smaller, the assembling of tubeparts has become progressively more difficult. Also, in tubes of theminiature type, due to the small size of the glass button stem, no exhaust 'tubulation is provided as the tube is exhausted from the top of the envelope. Until now, no provision has been made in these tubes for electrostatic shielding within the glass stem.

It is an object of my invention, therefore, to provide a vacuum tube having an improved shielding means which utilizes conventional tube structures and which can be inserted in the tube during a normal tube forming operation. It is thus a further object of my invention to eliminate specially designed structures for shielding the lead pins of vacuum tubes, as well as to eliminate the operations in assembling such shielding structures within the tube.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims, but the invention itself will be best understood by reference to the following description taken in connection with the accompanying drawing, in which:

a circle as shown in Fig. 2, for example.

. surface of stem l2.

Fig. 1 is a detailed view partly in vertical sectionor" a tube and shielding means according to my invention;

Fig. 2 is a cross sectional view taken along line IL-II of Fig. 1 looking in the direction'of the arrows;

Fig. 13 is an elevational view in vertical section of aglass button stem according to my invention; and

Fig. 4 is a detailed elevational View partly in vertical section of a tube and-shielding means according to a modification of my invention.

Referring to 1, there is partly shown an electron discharge tube -raon'ipri-sing a glass envelope it. One end of the envelope H! is closed by sealing thereto a round buttondike stem 12 shown in detail in Fig. 3. The envelope l0 encloses a plate M, a control electrode 16 and a cathode electrode l8. Sea-led through the button stem i2 and perpendicular to the faces thereof, area plurality of lead pins 2a, 322, 23, 24, 26 and 28. These lead pins are preferably arranged in The circle is usually concentric with the circular stem 12. The cathode I8 is connected to the lead pin 23 While the control electrode I6 and the plate electrode 14 are respectively connected to lead pins :26 and 24. Additional lead pins,such as 28, 22, 23 and '25, for example, may be provided to support internal parts of the tube structure or may be utilized as leads for additional tube electrodes.

At the center of the circle formed by the arrangement of the lead pins, there is sealed a shielding pin 30. This shielding pin extends through the glass stem 12 into the envelope of the tube. The-end of pin 30 is bent over at an angle to form a portion 32 extending above the Portion 32 is welded as at 33 (Fig. 2') to lead pin 28. Pin 28 forms a lead to the cathode electrode 48 usually from a radio frequency ground point external to the tube. However, pin 28 may form a lead to a shield electrode within the tube from a ground point in an external circuit.

In this arrangement pin 30 will act as an electrostatic shield between lead pins on opposite sides of the pin circle. Figs. 1 and 2 disclose lead pin 24 connected to ,plate [4 diametrically across the ,pin circle from lead pin 26 connected to control electrode l6. Pin 30 at the center of the pin circle effectively shields pin 24 from pin 26 within the glass stemportion 12. The short portion of pin-30 extending above the stem 12 and the bent p0rtion-32 continue to function as a shield between pins 24 and 25 in the region of the tube above the stem l2. However, the shielding field of pin til effectively shields pin 25 from any pin slightly displaced from either side of the plane of pins 26 and 39, such as pin 23 (Fig. 2). Furthermore, the shielding effect is not merely limited to the provision of an electrostatic shield between pin 26 and pins 23 and 24. It is clear that pin 38 passing through the stem l2 at the center of the pin circle also provides a shielding field between any pins on opposite sides of the circle. For example, within the glass portion of stem l2, pin 23%, shields pin 25 from pin 23 and also pin 29 from pin 22.

Bent over portion 32 of pin 30 provides a shielding field extending above the stem I2 and between leads arranged on opposite sides of portion 32. Thus, lead 25 above the stem I2, is shielded from leads 20, 23 and 24 (Fig. 2). This shielding field of portion 32 is similar to that provided by a vertical plate mounted in the same region. Portion 32 would also in varying degrees provide a shield between lead 22 or lead 25 and any one of leads 20, 23 and 24.

This arrangement of shielding pin 30 has been found to eliminate excessive coupling between the lead pins 24 and 25, respectively, of the output and input circuits. Furthermore, pins 20 and 22, for example, may also be used, respectively, as leads for the control and plate electrodes or for other electrodes which, if desirable, should be shielded from each other. I have experimentally found that such a pin 36 reduces excessive coupling and feed back at high frequency between the output and input leads and circuits of the tube.

Fig. 1 discloses shield pin extending through the lower surface of the disc-shaped stem l2 where it is cut off externally. However, pin 30 may also be formed as a center spud 34 welded within the glass stem i2 as shown in Fig. 3.

A further modification of my invention is disclosed in Fig. 4, which shows an electron discharge tube comprising a plate 40, a control electrode 42 and a cathode electrode 44 enclosed within the envelope 46. As in the modification of Fig. 1, the envelope 46 is closed at one end by a round glass button stem 43 sealed at its edges to the envelope. Similarly, there is arranged in the disc-like stem 43 a plurality of lead pins 50, 52, 54, 56 and 58 arranged in a circle concentric with the stem 48. These lead pins have short extensions projecting from the upper face of the stem 48 into the tube for attachment to the several electrodes. Projecting exteriorly from the lower base of the stem 48, the pins extend as long external leads which may be soldered into position in an external radio circuit. Lead pin 54 is connected to the cathode electrode 44 of the tube while lead wires 52 and 50 are connected to the control electrode 42 and the plate electrode respectively. To provide an electrostatic shield within the glass stem 48, I have sealed an additional lead wire 60 at the center of the circle formed by the other lead wires 50, 52, 54, 56 and 58. This lead wire may be grounded within the tube to lead wire 54 which is connected to the cathode electrode. One method of connecting shield wire 60 to the lead wire 54 is shown in the modification of Figs. 1 to 3. However, as shown in Fig. 4, the shield wire 60 is preferably brought out as a long external lead and may be soldered to a radio frequency ground point in the external circuit.

I have found that in the construction of the tubes of Figs. 1-4, that the shield Wires 30 and 60 may be of the same size and material as the other leads of the tube. Thus, it is not necessary to provide any specially constructed plate or other complex structures as a shielding means for the tube. Furthermore, it is evident that during the operation of sealing the lea-d pins into the glass stem, the shield pins 39 and 60 may also be sealed in the stem during the same operation. Thus, the other operations which were formerly required for fastening the shields in the tube have been eliminated. My invention provides a simple but effective shielding means for preventing interlead capacitances in the region of the stem. Furthermore, the simplification of shield structure and the elimination of shield assembling operations lowers the cost of tube manufacture.

While certain specific embodiments have been illustrated and described, it will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

What I claim as new is:

1. An electron discharge tube comprising an envelope, a anode electrode, a control electrode and a cathode electrode, said electrodes being mounted within said envelope, a circular button stem portion sealed to one end of said envelope, a plurality of lead pins sealed in and extending through said stem portion, said lead pins mounted in a circle, means connecting a first one of said lead pins to said anode electrode, means connecting a second of said lead pins to said control electrode, a shield pin sealed through said button stem portion at the center of the circle, means Within said envelope connectin said shield pin to said cathode electrode, said first and second lead pins being mounted in the same plane as said shield pin whereby said shield pin forms an electrostatic shield between said first and second lead pins.

2. An electron discharge tube comprising an envelope, 9. button stem portion sealed to one end of said envelope, a conducting pin sealed through said stem portion and having a part thereof extending into said envelope, a plurality of base pins sealed through said stem portion and extending into said envelope, said base pins mounted in spaced relation to said conducting pin, said conducting pin part connected to one of said base pins, a second and a third of said base pins being mounted in said stem portion opposite to each other relative to said conducting pin, whereby said conducting pin forms an electrostatic shield between said second and third pins.

3. An electron discharge tube comprising an envelope, a cathode electrode, a control electrode and an anode electrode, said electrodes being enclosed within said envelope, a glass disc-shaped stem portion sealed in one end of said envelope, a conducting pin sealed perpendicularly through said stem portion in the center thereof, a plurality of base pins sealed perpendicularly through said stem portion, said base pins mounted in a circle around the center of said stem, means connecting a first, a second and a third of said base pins respectively to said cathode, control and anode electrodes, said conducting pin extending Within. said envelope and welded to said first base pin, said conducting pin mounted in the plane of said second and third base pins, whereby said conducting pin forms an electrostatic shield between said second and third base pins.

4. A stem, for an electron discharge tube having an envelope, said stem comprising a flat circular disc for sealing to said envelope, a plurality of lead wires sealed through said disc in a circle concentric to said disc, a shield wire sealed through at least a major portion of the thickness of said disc at the center thereof, said shield wire having a portion extending from one side of said disc, said shield wire portion welded to one of said lead wires, a second and a third of said lead wires mounted on opposite sides of said circle relative to said shield wire, whereby said shield wire forms an electrostatic shield between said second and third lead wires.

5. An electron discharge device having a vitreous envelope, a plurality of spaced conductors sealed through the wall of said envelope, electrodes within said envelope and respectively connected to difierent ones of said spaced conductors, and a metal shield pin sealed in said envelope wall intermediate at least two of said spaced conductors electrostatically shielding said two spaced conductors from each other in said envelope wall.

6. An electron discharge device having an envelope, a flat glass button stem closing said envelope at one end, a plurality of spaced conductors sealed through said stem, electrodes within said envelope and respectively connected to difierent ones of said spaced conductors, and a metal shield pin sealed through at least a major portion of the thickness of said stem and extending within said envelope, said shield pin. positioned intermediate at least two of said spaced conductors and connected to one of said electrodes electrostatically shielding said two spaced conductors from each other.

7. An electron discharge device having an envelope, a flat button stem enclosing said envelope at one end, a plurality of spaced conductors serving at one end thereof as base pins sealed in a circle through said stem, electrodes within said envelope and respectively connected to difierent ones of said spaced conductors at the other ends thereof, and a metal shield pin sealed through at least a major portion of thickness of said stern and extending within said envelope in contact with one of said electrodes, said shield pin positioned at the center of said circle and intermediate at least two of said plurality of said spaced conductors electrostatically shielding said spaced conductors from each other.

8. An electron discharge device having an envelope, a plurality of conductors sealed through said envelope wall, electrodes within said envelope and respectively connected to di'iferent ones of said spaced conductors and a shield conductor sealed through at least a major portion of said envelope wall at a position intermediate at least two of said different ones of said spaced conductors, said electrodes including a cathode electrode connected to a third one of said spaced conductors, said shield conductor having a portion extending into said envelope, said portion being spaced from said two spaced conductors and connected to said third spaced conductor whereby said shield conductor provides an electrostatic shield between said two spaced conductors.

9. A stem, for an electron discharge tube having an envelope and electrodes therein, a plurality of spaced conductors sealed through said stem, said spaced conductors having short extensions projecting from said stem, a shield conductor sealed through said stem and having an eX- tension positioned intermediate at least two of said short extensions of said spaced conductors, a third one of said spaced conductors connected to the cathode electrode of said tube, said extension of said shield conductor bent at an angle thereto and connected to said third spaced conductor electrostatically shielding said two spaced conductors from each other.

10. A fiat glass stem for an electron discharge tube having an envelope and electrodes therein including a cathode electrode, a plurality of spaced conductors sealed through and perpendicular to said stern, and having extensions projecting from a surface thereof, a shield conductor sealed through at least a major portion of the thickness of said stem intermediate at least two of said spaced conductors, a third one of said spaced conductors to be connected to the cathode electrode of said tube, said shield conductor having an extension projecting from said stem surface and connected to said third spaced conductor electrostatically shielding said tWo spaced conductors from each other in the region of said stem.

THOMAS J. HENRY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,084,858 Metcalf June 22, 1937 2,205,502 Tromp June 25, 1940 

